Padding characters in printf

Question

Pure Bash, no external utilities

This demonstration does full justification, but you can just omit subtracting the length of the second string if you want ragged-right lines.

pad=$(printf '%0.1s' "-"{1..60})
padlength=40
string2='bbbbbbb'
for string1 in a aa aaaa aaaaaaaa
do
     printf '%s' "$string1"
     printf '%*.*s' 0 $((padlength - ${#string1} - ${#string2} )) "$pad"
     printf '%s\n' "$string2"
     string2=${string2:1}
done

Unfortunately, with that technique, the length of the pad string has to be hardcoded to be longer than the longest one you think you'll need, but the padlength can be a variable as shown. However, you can replace the first line with these three to be able to use a variable for the length of the pad:

padlimit=60
pad=$(printf '%*s' "$padlimit")
pad=${pad// /-}

So the pad (padlimit and padlength) could be based on terminal width ($COLUMNS) or computed from the length of the longest data string.

Output:

a--------------------------------bbbbbbb
aa--------------------------------bbbbbb
aaaa-------------------------------bbbbb
aaaaaaaa----------------------------bbbb

Without subtracting the length of the second string:

a---------------------------------------bbbbbbb
aa--------------------------------------bbbbbb
aaaa------------------------------------bbbbb
aaaaaaaa--------------------------------bbbb

The first line could instead be the equivalent (similar to sprintf):

printf -v pad '%0.1s' "-"{1..60}

Or similarly for the more dynamic technique:

printf -v pad '%*s' "$padlimit"

You can do the printing all on one line if you prefer:

printf '%s%*.*s%s\n' "$string1" 0 $((padlength - ${#string1} - ${#string2} )) "$pad" "$string2"

Pure Bash. Use the length of the value of 'PROC_NAME' as offset for the fixed string 'line':

line='----------------------------------------'
PROC_NAME='abc'
printf "%s %s [UP]\n" $PROC_NAME "${line:${#PROC_NAME}}"
PROC_NAME='abcdef'
printf "%s %s [UP]\n" $PROC_NAME "${line:${#PROC_NAME}}"

This gives

abc ------------------------------------- [UP]
abcdef ---------------------------------- [UP]

Trivial (but working) solution:

echo -e "---------------------------- [UP]\r$PROC_NAME "

I think this is the simplest solution. Pure shell builtins, no inline math. It borrows from previous answers.

Just substrings and the ${#...} meta-variable.

A="[>---------------------<]";

# Strip excess padding from the right
#

B="A very long header"; echo "${A:0:-${#B}} $B"
B="shrt hdr"          ; echo "${A:0:-${#B}} $B"

Produces

[>----- A very long header
[>--------------- shrt hdr


# Strip excess padding from the left
#

B="A very long header"; echo "${A:${#B}} $B"
B="shrt hdr"          ; echo "${A:${#B}} $B"

Produces

-----<] A very long header
---------------<] shrt hdr

There's no way to pad with anything but spaces using printf. You can use sed:

printf "%-50s@%s\n" $PROC_NAME [UP] | sed -e 's/ /-/g' -e 's/@/ /' -e 's/-/ /'

echo -n "$PROC_NAME $(printf '\055%.0s' {1..40})" | head -c 40 ; echo -n " [UP]"

Explanation:

• printf '\055%.0s' {1..40} - Create 40 dashes
  (dash is interpreted as option so use escaped ascii code instead)
• "$PROC_NAME ..." - Concatenate $PROC_NAME and dashes
• | head -c 40 - Trim string to first 40 chars